XNP Project Annual Report – Year 8

 

The "Xiphophorus – Northern Platyfish" project has been operating for eight years. If I stated here a year ago that we survived the seventh "critical" year without any problems, that is no longer true of the current development. The project is working, we are in touch with the members and we are doing what we can. But we have lost almost a thousand fish (!) and quite a few members remain in "stand by" mode, waiting for new fish or wanting to take a break themselves because they were not successful and do not dare (yet?) to try again.

 

Fish

Here are the numbers of fishes kept and how they evolve since the start of our project (as of the beginning of 2019, 2020, 2021, 2022, 2023, 2024, 2025 and 2026, respectively):

Xiphophorus meyeri Spotted:     434 - 645 - 1145 - 1436 - 1072 - 1041 - 1196 - 644

Xiphophorus meyeri Wild Type:  93 - 180 - 109 - 37 - 210 - 303 - 228 - 164

Xiphophorus couchianus:            114 - 180 - 438 - 664 - 765 - 850 - 836 - 492

Xiphophorus gordoni:                   29 - 63 - 56 - 18 - 27 - 70 - 14 - 66

Xiphophorus sp. "Apodaca":        12 - 0 - 0 - 0 - 0 - 0 - 0 - 0

Xiphophorus sp. "Regio":             19 - 110 - 83 - 86 - 49 - 106 - 117 - 84

Total number of fish:                    701 - 1178 - 1831 - 2241 - 2123 - 2370 - 2391 - 1450

The results are very worrying – no catastrophe has occurred and there is no immediate threat, but we have returned to somewhere in the 2nd or 3rd year of the project. We have previously recorded significant declines in the numbers of specific species, so far only Xiphophorus couchianus has avoided this. But now it is also one of the affected, the decline has affected most species and overall we have dropped from almost 2400 fish by a thousand.

Let's take a closer look at the individual species:

Xiphophorus meyeri Spotted: At the beginning of 2025 we had 21 breeders; 14 groups were breeding and thriving, some (even large) groups were having problems. A year later there were only 16 breeders and 11 thriving groups. With one exception (85), no group is larger than 70 individuals, which is worrying in itself – we used to have breeders with more than 100 individuals. The losses are mainly due to chronic diseases of the fish or due to technical problems. We knew about some of the problems earlier and now we are only being hit by the consequences.

Xiphophorus meyeri Wild Type: A year ago there were 9 breeders (5 breeding groups), now only 7 (3 really thriving groups). We lost four promising and still functioning groups completely, the breeders lost them and could not explain the reason. They are not easy fish, we know that, so there is no point in blaming or investigating anyone. But it would be a huge shame to lose this genotype. Fortunately we have 3, potentially 4 promising groups with enough individuals.

Xiphophorus couchianus: From 15 breeders a year ago, we now have 7! It is encouraging that all 7 groups are breeding and doing well. Most of the losses were expected, they were groups that were not healthy in the long term; in three cases, however, the extinction of the fish was a surprise (the causes were technical or unknown, the fish gradually died) and in two cases the loss was due to the termination of membership in the project. Specifically, one German breeder (the project members know his name) originally recevied X couchianus from the XNP project (of course for free)and reported 70 individuals at the beginning of 2025, but after being expelled for violating the rules, he refused to return them, or rather, he refuses all contact.

Xiphophorus gordoni: I mentioned here a year ago that it would be very desirable to obtain pure X. gordoni, because previously fish of dubious origin and identity had entered the project. Fortunately, this was achieved, so although the number of 66 does not seem to be significantly either up or down, it is in fact a great progress and at the same time a single group from a single breeder. Very prosperous and promising, so we hope for the continued success and gradual expansion of this species.

Xiphophorus sp. "Regio": This is a relatively difficult to breed platyfish (but which of the northern platyfish is not?). The situation is relatively stable, for several years we have had about 5 breeders and 3 really breeding groups, although they are not always the same ones. We must be very happy for them and we still need to find out how we can keep these fish better.

What about the overall "crisis"? There have been several fish transfers, but it is clear that we currently do not have a large supply of sources from which to take. It is necessary to continue trying new applicants, if they can pick up the fish. And to return to proven breeders, if they have been able to identify the cause of the failure and are determined to eliminate it. It is not advisable to underestimate the demands of northern platyfish, clean water and low temperatures are beneficial to long-term health, but it is not a universal key to unlocking success. Problems need to be actively fought, not waited for to disappear... it’s usually platyfish who inconspicuously disappear from our aquariums rather than their issues.

Last but not least, it is important to remember that our goal is to keep fish and preserve them for the long term. For some, this may be boring after a while, but it is important not to rest on our laurels and to always and “forever” try to provide the best care for the fish.

 

People

During 2025, the membership base changed only slightly - also because we do not have a current offer of surplus fish for new interested parties. One breeder from Germany and one club from France joined. On the other hand, 4 members left our project, some of whom after losing their fish and no longer interested in continuing, or due to communication problems.

The number of members who are not currently keeping any northern platyfish is increasing. However, they want to stay in touch, want to be members of the project and possibly become actively involved again later – when we find fish for them, but often also when they have more time, graduate, stop traveling, move, solve their own health problems, etc. This is completely understandable and there is no reason to completely cut off inactive members. However, since it is becoming increasingly difficult to do an annual census and renew contact with each project member and ask if he/she still wants to stay and if something has changed in his/her situation, it is desirable to separate active project members (= those who are currently keeping northern platyfish or will soon get them) and so-called associate members.

Here is the development of the total number of project members (at the beginning of 2019, 2020, 2021, 2022, 2023, 2024, 2025 and 2026): 18 - 23 - 28 - 42 - 51 - 52 - 47 - 45

Of the 45 project members, only 23 were keeping northern platyfish as of January 1, 2026.

Our members are currently from 9 countries: Belgium, Czech Republic, France, Hungary, Germany, Netherlands, Portugal, Austria, United Kingdom.

 

Information

Joined annual conference of Xiphophorus Working Group (XWG) and Goodeid Working Group (GWG) took place on October 3-5, 2025 in Gentbrugge, Belgium, with a great organization by the local aquarists. The afternoon block of lectures in the XWG section was completely focused on a single topic: Maintaining phenotypic traits in Xiphophorus in the long term and possible implications for conservation breeding. We talked about how Xiphophorus change in our aquariums and also a lot about genetics. The topic of “fresh blood” is still alive among aquarists, but it is not the only and probably not the best way to keep fish in the long term. This topic and the ongoing discussions are of course highly relevant to our project.

Complete list of lectures:

• Udo Wagenknecht and Dieter Gentzsch (VDA AK LAF, Germany): Development of wild form strains of Xiphos during long term keeping in aquaria
• Erwin Radax (Austria): Preserving species with different male sizes and types
• Markéta Rejlková (Ostrava Zoo, Czech Republic): Demographic and genetic management of ex situ populations in zoos and aquariums
• Lawrence Kemnitz (Germany) and Carsten Weile (Mexico): Aqua-Unity – Software for Species Conservation with Practical Examples
• Manfred Schartl (XGSC, USA and Würzburg, Germany): Long-term breeding and maintenance of Xiphophorus speciesat the Xiphophorus Genetic Stock Center, Texas State University, San Marcos, USA and at the Biocenter of the University of Würzburg
• Gil Rosenthal (University of Padova, Italy): What happens to natural diversity in hobby stocks, and how can we best preserve it?

It would be desirable to continue discussions on this topic and look for ways in which science can help us find effective ways to preserve species in the long term.

The XNP project was also presented (for the second time) in Thannhausen, Germany, in July 2025 at the 5th Conference on the Conservation of Species in Aquariums.

 

Project

A key event in 2025 was to be the transfer of X. couchianus and X. meyeri to Mexico, specifically to the public aquarium Acuario Inbursa in Mexico City. This transfer had been prepared between the Ostrava Zoo and the aforementioned institution since 2023, unfortunately in the spring of 2025, just a few hours before the fish were sent, it turned out that some documents were not in order and the Mexican side had to ensure their completion and new approval by the authorities. To date, this administrative obstacle has not been resolved, but hopefully it will happen soon. The exhibition of extinct Mexican fish is ready, only the fish are missing.

There was no change in the financial situation in 2025, i.e. all costs were paid by the relevant members individually and the project balance is zero, as are the total claims against ÖVVÖ to date.

 

Future plans

In 2026, we need to focus on improving the health of our fish, strengthening local breeder networks to facilitate fish transfers, and, last but not least, continuing dialogue with scientists on preserving genetic diversity and long-term maintenance of the species. We believe that we will be able to transport the fish to Mexico. However, the biggest goal is to stabilize the fish population and, ideally, to see it recover.

In 2026, the GWG meeting will be held in Mexico, so as an alternative to the European meeting, we are offering the 12th International Conference of Poeciliid and Goodeid Biologists, which will be held in Padua, Italy, from 16 to 18 July 2026. The first day will feature a special “hobby-science forum” where we will discuss conservation from all possible perspectives and, of course, above all, how hobby aquarists can get involved and what scientists have to offer.

 

Finally, as I do every year, I would like to thank all members of the XNP project again. You save rare species from extinction!

Markéta Rejlková

March 9, 2025, Ostrava, Czech Republic