Pighead prickleback COSEWIC assessment and status report: chapter 6

Biology

General

The pighead prickleback is a marine fish tolerating estuarine habitat. Their young probably spend early life drifting in midwater as planktonic larvae before settling on the bottom to feed on benthic invertebrates (Ratinsky 1983). The species is adapted to cold saline waters below sea ice in winter, and is adapted to living near estuarine and marine water in or below the holocline. The degree of their tolerance to intrusions of fresh and dilute waters is unknown.

Males outlive and outgrow females: males reach approximately 500 mm in length, and live up to 16 years of age, while females reach 470 mm in length and live up to 14 years. In Tuktoyaktuk Harbour newly hatched larvae and juveniles range between 15.8 and 21.5 mm in length (Ratynski 1983).

Reproduction

It is stated that pighead pricklebacks “seek” cooler and saltier water to breed (Species at Risk May 16, 2002). On the other hand, pighead pricklebacks at Tuktoyaktuk probably spawn during fall or winter when temperatures are already cold, holocline definitely shallower, and near surface waters more saline than in spring and summer when the Mackenzie River floods. Whether pricklebacks actively seek cooler and saltier water requires proof.

The average age of reproduction for pighead pricklebacks is approximately 9.5 years for males and females (calculation extrapolated from Hopky and Ratynski 1983). Females were found in August to have ova ranging from 1.0 to 1.4 mm in diameter (McAllister 1975); and by September to have nearly ripe ova (Ratynski 1983).

Year-to-year variation in year class strength (Hopky and Ratynski 1983) will affect population size and recruitment. A collection in 1981 in Tuktoyaktuk Harbour showed dominant age classes of 3, 6, and 13 years. 

Table 2. Length distributions, by sex, of various age groups of Acantholumpenus mackayi subsampled from 1981 Tuktoyaktuk Harbour catches (Hopky and Ratynski 1983)
Length (mm) 2 yrs
U
3 yrs
U
4 yrs
U
4 yrs
M
4 yrs
F
6 yrs
M
6 yrs
F
7 yrs
M
9 yrs
F
10 yrs
M
10 yrs
F
11 yrs
F
12 yrs
M
13 yrs
M
13 yrs
F
14 yrs
M
14 yrs
F
15 yrs
M
16 yrs
M
0-25                                      
26-50                                      
51-75                                      
76-100 2                                    
101-125 1 3                                  
126-150   7                                  
151-175   4                                  
176-200   2 1                                
201-125     1                                
226-250     1   1   2                        
251-275       1   1 4                1        
276-300             9                        
301-325           4 2   1                    
326-350           5   1     1        2        
351-375           3                  1   3    
376-400           1   1   1       1 4   1    
401-425                       2      1        
426-450                   2       2 1 1      
451-475                         1 6 1 1   1  
476-500                         1 2   1     1

Survival

Nothing is known about limiting factors to survival.

Physiology

Nothing is known about their particular physiology; however, they are assumed to possess physiological adaptations to withstand cold-water temperatures and survive long periods under ice in winter darkness. Their presence near estuarine conditions suggests that they possess an ability to adjust to salinity changes; however, their general distribution and circumstances of capture suggest that they are not adapted to conditions of pure freshwater.

Movements/dispersal

They probably disperse in response to underwater changes of salinity, turbidity, temperature gradients, summer-light and winter-darkness as they shift between shallower and deeper depths. Schetninnikov (1983) and Houston (1988) characterize the pighead prickleback as a non-schooling species. Doug Chiperzak (pers. comm. Dec 10, 2001) suggests that movements may be part of a migration between deeper and shallower waters.

Nutrition and interspecific interactions

Lacho (1991) found the following in stomachs of pighead pricklebacks (in descending order of occurrence):

  • unknown digested remains = 64;
  • polychaetes = 47;
  • oligochaetes = 35;
  • amphipods = 24;
  • copepods = 9;
  • plant remains = 8;
  • pelecipods = 6;
  • nematods = 5;
  • gastropods = 3;
  • bryozoans = 3;
  • mycideans = 2;
  • foraminiferans = 1

Many anadromous and estuarine fishes are found in the shallow waters where pighead pricklebacks migrate; marine fishes occupying the bottom habitat where the pighead prickleback primarily lives includes:

  • saffron cod - Eleginus gracilis
  • Arctic cod - Boreogadus saida
  • Fourhorn sculpin - Myoxocephalus quadricornis
  • Arctic flounder - Liopsetta glacialis;
  • starry flounder - Platichthys stellatus;
  • slender eelblenny - Lumpenus fabricius.

All tolerate estuarine conditions; however, the latter four are more often associated with bottom habitats. Presumably they all seek the more saline portions of estuaries, especially in and below the halocline.

Behaviour/adaptability

Other than clumped aggregations and movements over soft sedimented bottoms, there is little information on pighead behaviour. Large pighead pricklebacks have approportionally stout head with high snout and larger lips that suggest special behaviours used for reproduction, foraging or competition. Their eyes appear quite conspicuous and large and this may assist them in subdued light below the holocline during times when surface waters are iced over or clouded with river silt. In contrast, specialized species of pricklebacks adapted to living in the intertidal zone or amongst subtidal rocks have body forms suggesting that they are stronger swimmers (e.g., Lumpenus sagitta; Peden pers. observ. -- also see species accounts in Hart 1973 and Mecklenburg 2002).

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